Electromagnetic lens



Y Oct. 29. 1940. T. w. SUKUMLYN 2,219,405

ELECTROMAGNETIC LENS Original Filed Aug. 20, 1938 I'NVEN TOR.

Thomas H/ Salqm/yn BY AT TORNEY' 'Patnted Oct. 29, 1940 V ELECTROMAGNETIC LENS. Thomas W. Sukumlyn,.LosAngelesCalif. f Original application August 20, 1938, Serial N0..

Divided and this application April 17 1939, Serial No. 268,263 if 8 Claims. (01. 250-5161 This invention relates to a system for magnify- I ing images. V This application is a division of an application filed in the name of Thomas W. Sukumlyn on August 20, 1938, Serial No. 225,958, and entitled Electron microscope system. I I

The basis of magnification of this character is the'use of an optical lens system, for retracting light emanating from points .of the object, in 10 such a way as to focus diverging rays to build up an enlarged image. Itis well-known, however, that it is not possible to magnify the image indefinitely. There are inherent limits to the de-. gree of magnification by optics. I limiting factors is the'wave length of the light utilized for the illumination. It may be proved, for example, that with visible light, two points on an object to be magnified can beno closer than .00001 inch in order to appear as separate points of the enlarged image.

wave length in general, the smaller may be, this point separation and yet yield separate points on the enlarged image. It is one of the objects. of this invention to ob- 5 viate these limitations, and particularly by the utilization of suitable radiant energy of some form otherthanvi'sible light. I

Radiant energy for this purpose may be that provided by electronic emission. image, corresonding' to the object to be enlarged, may be formed by the electrons on a fluorescent screen; or alternatively the electrons may affect a sensitive photographicsurface. The stream of electrons is controlled to delineate the image;

' and for this purpose use is made of devices intended to bend the electron rays in a manner- I analogous to the refraction of visible light byan optical system It is another object of inventio topic-j vide; devices of this character, which may. be'

aptly termed electron ray lenses. [The simplest manner of practicing.

so. tion to make it possible .to transmit a. beam of electrons to affect a suitable screen and to form thereon an enlarged ormagnified image of an object cooperating with the beam.

This invention possesses many other advari s. n s qt g vbie -iw i m bsm One of the I The shorter the vergesin passing A magnified manner.

I I the invention is by rendering the object electron emissive.

However.

more easily-apparent from *al-eonsiderationof several embodiments of thepresent invention.

For this purpose thereare shown a few forms in the drawing accompanying and forming'part of. I the present specification. These forms-which 52- illustrate the general principles of my invention,- will now be; described :in" detail; but itis" toqbe understood that thi's detailed description isnot to be taken in a limiting sense, since the scope of myinvention is best defined by thev appended 10"} claims I Referring to the drawing: z Figure l is a diagram, illustrating .aks'ystem embodying my invention;- I

Fig. 2 is a pictorial view of one of the electron 15 ray lenses;

' Fig. 3 is adiagram'illustrating the function of: the electron ray lens illustrated: in FigJZQand also showing the lens in longitudinal'sectionj Fig. 4 is an endview of theelectron ray lens 0 illustrated in Fig. 2, and

Fig. 5 is-a'view similarrto Fig. 30f a form of electron .ray lens in whichthe electron raydi through the lens instead ofconverging as in the form illustrated in- Figs. 2, 25

I 3 and 4.

In FigureL-a conventionally shaped object I is illustrated as the objector which it is-de-' sired to form an image by the aid of electronic emission; As an example of one way'in which 30 this electronic "image may be formed, object I' may be made inherently emissive in any suitable.

For example, the object I may be coated on its front surface with a layer 2 of radio-active material. Such a coating may be obtained in any well known manner, such for eX- ample as exposing the object 1 to radioactive material or to radium emanation, Electrons are liberated from the coating 2 andzfinallyythe' beam of electrons corresponding to the object [II isj 0 focused to an image; in this. instance, on'a screen. 3; This screen 3 may be fluorescent in order to produce immediately a visible image, .or'else a photo-sensitive layer may-,be' provided to be affected actinically. I

The forming-or focusing" of the image involves the use of retracting devices-intervening between the object I and the screen 3. The object :I is

disposed inv conducting relation to. a conducting support 4. A pair of annular or tubular devices so i i 5 and 6 are next placed in the path of the elec-. tron stream. These devices 5 and 6 are provided: with apertures and B respectivelyv for confining, theelectron beam 9 emanating from object 1 in a co r r i lrna w pa h-sailor.thisrur ose- ,5,.-

the members 5 and 6 are maintained at a potential positive with respect to the object I as by the aid of the batteries and II. These devices and 6 may be termed electro-optical lenses for acting upon the electrons to confine them into a small bundle.

The electron beam 9 conforming to the object I is next acted upon by accelerating anode l2. This acceleratinganode I2 is maintained at a positive potential with respect to object I by the aid of the additional battery I3.

Located in the path of the beam 9 as it emerges from the directing or accelerating anode [2 are a pair of electron ray lenses [4 and I5, forming a ray refracting system. These are substantially analogous to refracting optical lenses. Thus lens I4 is the equivalent of a convex'or converging lens structure, while lens 15 is the equivalent of a concave or diverging lens structure for the beam 9. lenses will be described presently. For the moment it is suificient to note that each of these lenses is in the form of a series of conductors arranged toprovide magnetic fields through which the beam 9 must travel to reach screen 3. Thus lens N forms a magnetic field annularly disposed around the axis l6 of the lens. This'annular field in this instance is shown as having increasing length as the radius increases from the axis l6. This is represented by the triangular section bounded by the crossing lines 11 and IS, the crossing occurring on the axis [6.

Accordingly, the rays comprising the electron beam 9 are deflected more and more as they depart from the axis Hi. This deflection occurs due to the well-known action of a magnetic field upon electrons. In other words, this magnetic field serves in a manner analogous to a converging optical lens inits operation upon the electron 1 beam 9.

Analogously, the electron ray lens I5 is arranged in reverse manner; that is, the length of the annular magnetic fieldis a maximum along the axis I6 and its length decreases as the radius increases from this axis. Thus the electron beam 9 is diverged by this lens structure [5.

By appropriate positioning and design of the lenses l4 and I5, they form a proper refracting system. The action upon the beam 9 is that the beam is focused 'to cause an image to be visible on the screen 3, either by fluorescence or by development of the photo-sensitive surface.

As illustrated, the screen 3 is maintained at a potential positive with respect to the object I in order that the electrons may be attracted thereon. Also, the structuresl4 and I 5 may be connected to the system so as to be maintained at a positive potential.

It will be understood that all of the apparatus is to be inclosed in an appropriate, evacuated vessel.

The electron ray lenses are shown in detail in Figs. 2 to 5 inclusive. In the structure illustrated in Figs. 2, 3 and 4, theeifect of the electron ray lense is to converge rays of electrons. For this purpose use is made of 'a pair of terminal collars 51 and 58 placed coaxially with respect toa lens axis 63. Each of these terminal collars may carry enlarged flanges such as 59 and 60 connected to opposite poles of a battery 61 or other source of electrical energy. These flanges 59 and 60 ensure that there be no appreciable variation in the resistance through the various conducting paths now to be described. These conducting paths are formed of conducting tween the internal surfaces The specific structure of these two elements such as 62 forming virtually elements of a double cone, the bases of which, are oppositely directed and the apices of which fall upon the axis 63. It is seen, that current flows from battery 6| first of all to the terminal collar 58; thence from the base of one cone element through all of the conductors 62 in parallel, and finally to the base of the left hand cone, into the terminal collar 51, and to the negative side of the battery 6|. The resultant magnetic field is such that in the annular area beof collars 57, 58 and the equivalent cone surfaces, there is a strong magnetic field directed downwardly in the upper part of the figure as indicated by the cross 64, and upwardly as indicated by the dot 65. The magnetic field is confined to the space between cylinder and cone and is everywhere perpendicular to the axis.

I Assuming that there are two electron rays 66 and 61 emerging from a common point on an object, these rays are bent downwardly and inwardly toward the axis to be focused at a common point 58. The ray 66 which is farther from the axis 63 than the ray 61 is refracted to a greater extent because it travels through a longer magnetic field.

A refracting lens structure for diverging the electron ray is illustrated in Fig. 5. In this case the terminal collars 69 and are fed from a battery II. The conductors 12 form virtually the elements of a cone, and are attached at the base of the cone to the outer edge of the terminal collar 16. A similar set of conductors 13 is arranged in connection with the terminal collar 69. The two sets of conductors 72 and 13 are connected by conductor 74. The axes of the cones coincide with the axis of the lens structure.

In this case the annular magnetic field resulting from the current flowing through conductors 12 and 73 has a diminishing width. The section of the annulus is defined by the elements of the enveloping cones and by the internal surfaces of the collars 69 and 16. Accordingly the farther away an electron ray is from the axis 15, the shorter its path through the magnetic field. The resultant effect is to diverge the rays.

Itis not necessary that the conductors 62 or 12 be straight, as shown. They may be appropriately curved to cause the amount or extent of refraction to differ in a desired manner from that produced by a straight conductor. case, the envelope of the conductors will be defined by a surface of revolution about the axis 63 or 14, other than the surface 'of a cone. I It isclearthat by appropriate design and appropriate location of one or more electron ray lenses such as now described, the electron rays may be treated in substantially the same manner as light rays by optical refracting systems.

By appropriate choice of current polarities flowing in the elemental conductors 62, the lens of Fig. 3 may be converted to a divergent lens; and similarly; appropriate changes in the connections to and from the cones and rings of Fig. 5, this lens may be made converging.

What is claimed is:

1. An electromagnetic lens for magnetically defleeting rays of electrons, said lens having a longitudinal axis, as well as a plurality of conductors arranged around the axis, and a source of direct current for the conductors, said conductors having a direction oblique to the axis and converging toward a common point on the axis, and connected across the source for passing currentv through the conductorsgto form an annular mag- I netic field about the axis, the width or the field m -the direction of the axis'being non-uniform,

whereby the length of the path of a ray'of electrons through theannular field is a function of the displacement ofthe ray from the lens axis. 2. An electromagnetic lens 'for magnetically deflecting rays of electrons, 'said lens having a longitudinal axis, as well as a plurality of conductors forming converging elements of a cone having its apex on the axis, and a source of direct current for passing current through the conductors in a uniform direction toward or from the cone apex.

: tors forming elements ofv a double cone, the apex 3.'An electromagnetic lens for magnetically deflecting rays of electrons, said lens having a longitudinal axis, as well as a plurality of conduc- I of the cone falling on the lens axis, and a source of directcurrent for passing current through the conductors in auniform'direction between the bases of the cone.

- "4. An electromagnetic lens" for magnetically deflecting rays of electrons, said lens having a longitudinal axis, as well as ,a' pluralityof con ductors forming elements of a double Come, the apex of the cone falling on the lens axis, conducting rings forming the bases of the cones to which the respective ends of the conductors are electrically connected, and a source of direct current. having its opposite terminals respectively f connected to said rings.

a 51- An electromagnetic lens for magnetically deflecting rays of electrons, said lens having a longitudinal axis, comprising a pair of conducting rings coaxial with said axis, a pair of series I 0f conductors,respectivelyelectrically connected "I to the rings, each of thepair oi series'forrning the elements of a'cone, with its apex falling on the axis, the apices of the cones beingcppositely directed, an electrical connection between the said rings. ,g

6. An electromagnetic lens ,for magnetically v deflecting rays-of electrons, said lens havingja longitudinal axis, comprising a plurality of con-. 7 f

ductors oblique to the axis, and arranged in parallel electrical relation, the envelope of said conapices, and a source of direct current having its opposite terminals connected respectively to the ductors being defined by a surface of revolution aboutthe axis, and a source of direct currentfor passing current in parallelto all of thefconducw tors; 1,. An electromagnetic lens for magnetically deflecting raysof electrons, said lens having a longitudinal axis, comprising a pair of conducting rings spacedalong the axis and coaxial therewith, a plurality of conductors electrically" joined respectively at their endsto said rings, and intersecting the axis, the envelope of the conductors being defined by'a surfaceof revolution about the axis, and a source of direct lcurrent having its terminals connectedto the rings Q q 1 8. An electromagnetic lens for magnetically longitudinal axis; comprising a series of conductors and a source of direct current 'for the'conductors, said conductors being connected across the source for passing current through the conductors, and being soplaced that there is a re-' sultant magnetic :field'of annular formcoaxial with the axis, the width ofthe. annular field along apath direction parallel to the axis being a function of the distance of the path fromthe axis.

deflecting rays of electrons, said'lens having a THOMAS W. SUKUMLYN, 

